OSCA is a system variable of the uc_osca user class. It can be used in a client 4GL application, a server 4GL application, or both at the same time when, for example, an OpenROAD Server application is a client to another application. In the latter case, OSCA errors can be checked with method CheckAndHandleError in the usual manner. By default, errors get passed up the chain of called applications. User procedures for fatal errors and user errors can be written that override the default behavior. For more information, see CheckAndHandleError Method (OpenROAD Client) (see CheckAndHandleError Method (OpenROAD Client)).